The attack is reportedly one of the deadliest on civilians in Egypt's modern history.

Islamist militants attacked a Sufi mosque in Egypt on Friday, killing at least 235 and wounding at least 130 people, according to the Associated Press and The New York Times.

The attack, reportedly one of the deadliest on civilians in Egypt's modern history, happened at a mosque in the North Sinai town of Bir al-Abed, 125 miles northeast of Cairo.

Though no one has taken credit for the attack yet, the militants are believed to be affiliated with ISIS, which considers the Sufi Muslims heretics. Egypt has also been fighting the ISIS' North Sinai branch since 2013.

How the attack unfolded

About 1:50 p.m. local time, dozens of militants riding in jeeps detonated at least two bombs inside the Sufi mosque in the North Sinai town of Bir al-Abd. The militants set up ambush locations and opened fire on worshippers as they fled the church and on ambulances as they arrived to treat and transport the wounded.

By 2:30 p.m., the Associated Press reported that at least 54 had been killed and 75 were wounded. Most of the wounded were taken to the general hospital in the nearby town of El Arish, where hospital workers described a chaotic scene, The Times reported.

"They pretty much have bullets in every part of their bodies," one medical official told The Times, adding that some lost limbs or were badly burned.

Images were soon posted on social media of bloodied bodies wrapped in sheets on the mosque floor and of family members outside the hospital as ambulances raced back and forth.

Egyptian President Abdel Fattah el-Sisi convened a national-security meeting before declaring three days of mourning, The Times reported. Sisi also said in a statement that the "attack would not go unpunished" and that "justice will be served against all those who participated, contributed, supported, funded, or instigated this cowardly attack," according to Reuters.

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US President Donald Trump tweeted at 10:27 a.m. ET on Friday that "Horrible and cowardly terrorist attack on innocent and defenseless worshipers in Egypt. The world cannot tolerate terrorism, we must defeat them militarily and discredit the extremist ideology that forms the basis of their existence!"

Egypt's military has begun conducting air strikes in the mountainous areas of North Sinai where the militants are believed to hide out, Reuters reported.